Lattice imaging study of a martensite-austenite interface

Abstract

The lattice planes up to, and through, a martensite-austenite interface are revealed directly for the first rime by the high resolution, lattice image technique of transmission electron microscopy. Both conventional and unique data may be derived by suitable analysts of such images. Thus, in the shape memory alloy NiTi, the orientation relationship and habit plane are found to be identical to those established by conventional experiments. The two phases are seen to be fully coherent at the end of the growing martensite plate with the first interfacial dislocation occurring about 260 A back from the plate tip. Lattice distortions adjacent to the plate are detected but no significant features are demonstrated at the end of the plate where growth had ceased. Characteristic premartensitic contrast could not be associated with significant static lattice displacements. Whether or not transformation dislocations exist in the martensite-austenite interface requires further, more detailed investigation.